Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 302011
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
311 PM CDT Sat Aug 30 2014

.SHORT TERM...(This evening through Sunday)
ISSUED AT 310 PM CDT SAT AUG 30 2014

1847z radar imagery shows a broken line of showers beginning to
develop along the I-55 corridor. 12z NAM has a great handle on the
location of the convection, but is about 3-4 hours too slow.
Meanwhile, the HRRR seems to be doing good on both the location and
timing.  Both models develop scattered storms over the next couple
of hours along the I-55 corridor and basically keep them in that
general area through early evening before dissipating them toward
midnight.  Based on latest radar trends, will focus likely PoPs
along I-55 through the afternoon, then will gradually shift them
eastward toward I-57 by evening.  Further east and south, will only
carry chance PoPs this afternoon through tonight as storms should
tend to weaken as they slowly track eastward later this evening.
Partial clearing will take place across mainly the western half of
the KILX CWA tonight.  With plenty of low-level moisture in place
and winds diminishing to 5 mph or less, think patchy fog will
develop overnight. Sunday still appears to be a largely dry day,
with perhaps a few showers/thunderstorms lingering across the far
E/SE.  High temperatures will top out in the middle 80s.


&&

.LONG TERM...(Sunday night through Saturday)
ISSUED AT 310 PM CDT SAT AUG 30 2014

Main issue in the mid range of the forecast is the general slowing
of the next system for Sunday night/early Monday morning.  For now,
Sunday remains dry and the pops start to sneak into the forecast
after midnight Sunday night and spreading into Monday and Monday
night. Mondays fropa will be accompanied with a threat for potential
severe weather.  SPC has Illinois north of I-70 and down into MO and
eastern Kansas in a Day 3 Slight Risk.  Increasing instability with
plenty of moisture in a very warm airmass for Monday before the
frontal passage in combination with deep shear will lend itself to
the potential for severe weather. Timing shifts in the models so far
will likely keep the forecast somewhat conservative.  Monday night
keeping the precip through the overnight and so far, the models
lingering some precip in the morning on Tuesday, though the 12z runs
are speeding that up as well.  Future forecasts likely to see
Tuesday afternoon dry out as well. GFS still sending an MCS for
Wednesday, and being somewhat aggressive with the precip, whereas
the ECMWF is drier for now.  The AllBlend keeping slight and chance
pops through day 7.  Another boundary headed into the Midwest for
late in the week as a wave crosses over the US/Can border...but
heading into quasi zonal flow aloft not really supporting any major
progression of the sfc boundary. Slow boundary pointing to yet another
pd of being just on the edge of the unsettled weather with a signif
lack of 500mb height gradient over the southern half of the CONUS.
Thermal ridging in the south keeps above normal temps over the
region.


&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
ISSUED AT 1236 PM CDT SAT AUG 30 2014

Robust Cu-field continues to develop between the Illinois River
and I-55 early this afternoon: however, 1728z radar imagery
remains clear. As instability slowly increases, am expecting
scattered thunderstorms to develop along this corridor after
19/20z. Given timing and areal coverage uncertainties, have
included VCTS at all terminals beginning at 18z. As the afternoon
progresses, think main area of concern will shift east of the
Illinois River Valley, so have dropped VCTS at KPIA after 22z.
Further east, will maintain thunder mention through 05z, allowing
plenty of time for any diurnally driven storms to dissipate after
sunset. Once convection ends, skies will partially clear and winds
will become quite light overnight. Forecast soundings and numeric
guidance both suggest patchy fog, particularly across the western
KILX CWA where winds will be lightest. As a result, have included
reduced visbys down to 2-3sm between 09z and 13z.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...BARNES
LONG TERM...HJS
AVIATION...BARNES





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